1. Field of the Invention
This invention relates to a method and apparatus for running an engine and associated powertrain in a motor vehicle in the same manner as a normal road operation, while maintaining the body of the vehicle stationary, for various testing purposes.
2. Prior Art
U.S. Pat. No. 4,121,452 issued to Wakabayashi et al discloses a microprocessor-based diagnostic testing system for periodic safety and emission testing of automobiles. U.S. Pat. No. 3,926,043 issued to Marshall et al discloses an automatic driver system for diagnostic testing wherein the throttle actuator 54 is moved in response to an output from a recorder 44. A position feedback is provided by means of a potentiometer 48. The dynamometer is also controlled by the system recorder 44 and includes a device 42 which contains an eddy current inductor which provides a retarding force on the ruler 34.
U.S. Pat. No. 3,333,463 to Hollinghurst discloses a dynamometer system wherein braking is applied by means of the dynamometer brake to correspond to the use of the actual vehicle brake. Hollinghurst also teaches a feedback control loop supplying information about vehicle speed and accelerator pedal position. However, there is not taught a triple loop control system including a feedback signal characterizing the speed of actuator movement. None of the background art teaches both an accelerator pedal position feedback signal and a servo motor speed feedback signal.
The patent to Campbell, U.S. Pat. No. 3,712,126 teaches a digital proportional and derivative control while the patent to Hollinghurst teaches an analog proportional control. However, no uncovered background art discloses the use of any analog controllers employing the three control modes of proportional, integral and derivative.